Utility poles (a designation which is intended to include lighting poles, power transmission poles, sign supporting poles or any similar structure) are generally too tall conveniently to be scaled by ladders. Nor is it always convenient to use a mechanical, hydraulic or pneumatic power lift, such as the well known "cherry picker" bucket.
Historically, when virtually all utility poles were made of solid wood, the poles were climbed by linemen provided with "climbers" having an L-shaped, metallic frame that could be strapped onto the lineman's foot and lower leg to present a laterally extending, downwardly directed spur that could be driven into the pole by the application of pressure to the L-shaped frame by the lineman's foot. Sequential insertion of the spur on the "climber" worn on one leg and then the climber worn on the other leg permits a lineman to walk step-by-step up the pole. The use of climbers requires considerable strength and skill, but even the most accomplished lineman can encounter a location along the length of the pole which will not properly secure the spur to support the weight of the lineman and may, therefore, allow the spur to "break out." Even with a safety strap, or belt--which should preclude a complete free fall--the lineman may find himself sliding down along the pole against the brutal action of the upwardly directed splinters.
Eventually, utility poles were provided with permanent steps that were driven, or screwed, into the pole at spaced distances along the vertical extent of the pole. Such permanent steps would permit a lineman to ascend the pole with little more effort than climbing a ladder. Generally, the lowermost of the permanent steps would be located at a height which could not conveniently be reached from the ground, but could be reached by using the previously described "climbers" or by a relatively short ladder. In any event, there was always the threat of enticing an unauthorized person to scale to the first step and then easily climb the pole with its attendant dangers to the unskilled.
Demountable step members were the next phase in the progression, and demountable step members have been available for use on wooden utility poles for many years. Demountable step members for wooden utility poles were secured to special nails that were permanently driven into the wood. Such an arrangement, however, is not usable on hollow utility poles inasmuch as the special nail derives its supporting ability by being almost fully inserted into a solid member.
Attempts have been made to secure the head of a special bolt interiorly of the hollow utility pole with the threaded shank portion extending radially outwardly through the wall of the pole and then tightening a stamped metal plate onto the threaded shank with a nut and washer so as to permit demountably securing a step member to the mounting plate. Because the walls of hollow utility poles do not always have a constant, predetermined thickness, this approach requires the use of bolts having a sufficient length to accommodate a wide variety of wall thicknesses. The use of bolts which are longer than absolutely necessary itself induces inherent flaws. First, if the threaded shank portion has any excessive length, that excess length poses a potential hazard in that it tempts reckless individuals to try and climb the pole without using demountable step members. Second, were one to sever any excess length from the shank portion after the bolt has been installed, that act would damage any protective galvanizing coating that may have been applied to the bolt. Third, the excessive length of the threaded shank portion on each bolt constitutes an undesirable protuberance which can snag the safety belt, tool belt or even the clothing of an accomplished line man.